LITTLE ROCK (AP) — Members of Arkansas' congressional delegation said Friday they want federal wildlife officials to reduce the size of a proposed "critical habitat" area for two types of rare mussels.

The U.S. Fish and Wildlife Service in September proposed designating 769 miles of streams as critical for the Neosho mucket and the rabbitsfoot mussel. The agency said the Neosho is endangered and the rabbitsfoot is threatened, making it illegal to kill, harm, harvest or possess them.

The mussels are considered indicators of good water quality. A wildlife service representative last year referred to them as "the canary in the coal mine."

In a letter dated Thursday and released Friday, Arkansas' senators and four congressmen said half of the rabbitsfoot critical habitat area falls in Arkansas and that 42 percent of the state could be affected by new regulations intended to protect the mussels.

After the members of Congress released their letter, the Fish and Wildlife Service said they were exaggerating the problem. They said the designation covers 8 percent of Arkansas' stream miles — not land area.

"In addition, for most landowners, the designation of critical habitat will have no impact," the Fish and Wildlife Service said in a statement. "It will not prohibit a farmer from allowing cattle to cool down in a river, or from driving a vehicle through a stream on their property."

The members of Arkansas' congressional delegation also questioned whether the designation was science-based and considered the economic impact on farmers, communities, governments and businesses.

"Due to the scope of the proposed critical habitat designations, the potential impact on Arkansas and other states, as well as the flawed process through which the proposal was formulated, we urge a reconsideration of and reduction in the size of the proposed critical habitat designations for the target species," reads the letter, which was signed by all six members of the delegation.

The Fish and Wildlife Service says the mussels' habitat is being threatened by channelization, chemicals, mining and sedimentation. It said a final decision on the size of the area will be issued in March.

The Neosho mucket is found in parts of Arkansas, Kansas, Missouri and Oklahoma. The rabbitsfoot is found in parts of 14 states.